The purpose of this study was to investigate whether changes had occurred in attack rates in primary teeth during the 1980's. Data on decayed and filled surfaces (df) in 5-9 year old children from the 1979-80 and 1986-87 NIDR dental caries surveys were analyzed. The attack rate was defined as the number of decayed and filled surfaces per 1000 surfaces at risk. The prevalence of df surfaces declined from an overall mean of 5.31 in 1979-80 to 3.91 in 1986-87. Surface-specific caries attack rates were found to be similar in both surveys. The rank order of the largest six attack rates were: occlusal surfaces of 2nd and 1st molars, distal surface of lst molar, mesial of 2nd molar, lingual of upper 2nd molar and buccal of lower 2nd molars. The tooth-specific attack rates were, from high to low: 2nd molar, 1st molar, central incisor, lateral incisor and cuspid. There was no appreciable difference reduction in caries attack rates between the occlusal and proximal surfaces of primary teeth from the 1980 to 1987 NIDR survey. This was in contrast to greater reductions in caries attack rates reported in proximal surfaces of permanent teeth between the 1971-74 HANES survey and the 1980 NIDR survey and also permanent teeth between 1980 to 1987 survey.